Many industries, and more particularly the automotive industry, utilize stackable bins employing collapsible sidewalls for transporting components or articles, particularly when such transporting requires shipment by carrier such as a truck from a first location to a distant second location. Stackable bins of the type commonly utilized employ upper and lower supports or pallets which are conventionally vacuumed form of heavy plastic material, with a tube-like sidewall structure being removably positioned between the upper and lower pallets to define an enclosed compartment for the goods being transported. A plurality of such bins are then typically vertically stacked on top of one another within the truck or other transport vehicle. Due to the heavy loads which are transported within these storage bins, and the fact that several such bins are vertically stacked on top of one another, hence requires that the tube-like sidewall structure be capable of withstanding significant loading, particularly vertical compressive loading.
In addition to the loading requirements, these bins must also be readily folded and compactly stored when empty so as to facilitate return shipment while occupying only minimal space. For this purpose, one commonly utilized sidewall structure employs sheet-like parallel side walls hingedly joined at the ends thereof to sheet-like end walls. The end walls have a central vertical hinge so that each end wall functions as a bi-fold and can be folded inwardly between the sidewalls to permit substantially flat collapsing and storing of the sidewall structure. This type of collapsible sidewall structure is commonly referred to as a "six-fold".
This six-fold sidewall structure is conventionally formed of a wall structure created by laminating several layers of corrugated paper board together. That is, the side and end walls typically are formed by three corrugated layers of paper board adhesively bonded together so that the resulting wall structure is of a multi-ply construction so as to provide increased strength and rigidity. This multi-ply construction also forms the corner hinges and the center end wall hinges, which hinges typically are defined by score lines. While six-folds constructed of laminated paper board are well known and widely utilized, and are advantageous in view of their minimal cost, nevertheless they also possess recognized disadvantages. A primary disadvantage of the six-fold employing laminated corrugated paper board is its extremely short life. Users of this type six-fold have discovered that such a six-fold can only be used a small number of times, typically three to five loading-and-return cycles, before the six-fold experiences sufficient deformation and damage as to require its disposal. This type of six-fold is also of limited vertical stacking strength and, when dealing with extremely heavy loads, is often unsuitable since the thickness of the wall structure cannot be increased in view of the limitations imposed by the pallets. Further, this type six-fold is subject to damage due to its exposure to moisture, grease and the like.
In an attempt to provide an improved six-fold sidewall structure, one modification has been proposed wherein the walls are formed by bonding together several layers of corrugated plastic, with the corner hinges between the end and sidewalls being created by a vertically-extending mill cut. This sidewall structure as formed solely from several corrugated plastic layers, however, has proven to possess several disadvantages. To begin with, this sidewall arrangement is much heavier than a paper six-fold and, since weight is of importance when shipping product, it is hence desirable to maintain the weight of the bin at a minimum. Another disadvantage is that this plastic six-fold does not possess adequate stacking strength since any distortion or misalignment results in the sidewall arrangement being loaded in a manner which is less than optimum relative to the corrugated structure of the sidewalls, and hence can cause collapsing or failure under load. This plastic six-fold is also much more costly to manufacture than a paper six-fold. The manner in which the plastic six-fold is provided with a milled slot defining the corner hinge is also believed to create a significant weakness. Hence, this plastic six-fold has proven to possess little, if any, advantage over the paper six-fold and thus has had only limited commercial acceptance.
Accordingly, it is an object of this invention to provide an improved collapsible six-fold sidewall structure for a stackable bin, which sidewall structure possesses structural and functional features which significantly overcome many of the aforementioned disadvantages.
More specifically, this invention relates to an improved collapsible sidewall arrangement of the six-fold type for use in a collapsible bin, as aforesaid, which sidewall arrangement is capable of providing increased stacking strength and hence increased vertical loading capability, is capable of providing greater strength for resisting distortion or deflection of the sidewalls due to distortion caused by loading either externally or internally, is of relatively light weight so as to not significantly affect the overall weight or payload which can be carried by the bin, is resistant to moisture and other liquids, can be successfully utilized for a large number of transporting load cycles (such as up to 100 loading cycles) prior to requiring replacement, and is more economical to purchase and utilize when evaluated on the basis of cost versus life.
In the improved six-fold sidewall structure of this invention, the side and end walls are each of a multi-ply laminate, preferably a three-ply laminate. The laminate includes inner and outer layers which coextensively overlie and are adhesively secured or bonded to opposite sides of an intermediate or middle layer. This middle layer comprises a thin sheet of rigid plastic foam such as expanded polystyrene which is of rather low density so as to provide the side and end walls with extremely high compressive strength for purposes of vertical stacking. The inner and outer layers are generally substantially identical and each is formed by a plastic layer having parallel inner and outer facing sheets rigidly joined together by a plurality of ribs which define therebetween a plurality of parallel channels which run between the facing sheets. These plastic layers are preferably formed from plastic such as polyethylene or polypropylene, and may be an extruded profile or laminated corrugated construction. These plastic layers, by being bonded to opposite sides of the expanded foam layer, cooperate therewith to provide the walls of the sidewall structure with the durability required to withstand the side loads which are applied to the sidewall structure and provide significantly greater side distortion strength.
In addition to the laminated construction associated with the six-fold sidewall arrangement as explained above, this sidewall arrangement also utilizes one of the plastic layers, generally the outer layer, to function as a hinge both for the bi-fold endwalls and for the corners.
Other objects and purposes of the structure according to the present invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.